THE INFLUENCE OF DEPRESSION ON COGNITION IN PARKINSONS-DISEASE - A PATTERN OF IMPAIRMENT DISTINGUISHABLE FROM ALZHEIMERS-DISEASE

Conflicting reports about the effects of depression on cognition in Pa rkinson's disease (PD) are difficult to interpret because they are bas ed on small sample sizes and confound depression with other variables. We found that a sample of 45 PD patients with current depression was cognitively more impaired than a sample of 45 PD patients without curr ent depression matched for age, education, gender, age at disease onse t, disease duration, and disease severity. The domains of cognition im paired in the two PD groups (compared with 45 age-, education-, and ge nder-matched controls) overlapped considerably, but (only the depresse d PD group had impaired memory relative to the control group. Our comp arison of 22 depressed PD patients and 22 Alzheimer's disease (AD) pat ients matched for overall severity of cognitive impairment, age, educa tion, and gender indicated that the depressed PD group performed signi ficantly worse on visuoconstructive tasks and marginally worse on conc eptualization tasks. In contrast, the AD group performed significantly worse than the depressed PD group on memory tasks. Together, our resu lts suggest that depression has a negative impact on cognition (and, i n particular, memory) in PD, and that the pattern of this cognitive im pairment is distinguishable from that associated with AD.